Time-Reversal Division Multiple Access over Multi-Path Channels

Abstract

Abstract-The multi-path effect makes high speed broadband communications a very challenging task due to the severe intersymbol interference (ISI). By concentrating energy in both the spatial and temporal domains, time-reversal (TR) transmission technique provides a great potential of low-complexity energyefficient communications. In this paper, a novel concept of timereversal division multiple access (TRDMA) is proposed as a wireless channel access method based on its high-resolution spatial focusing effect. It is proposed to use TR structure in multi-user downlink systems over multi-path channels, where signals of different users are separated solely by TRDMA. Both the single-transmit-antenna scheme and its enhanced version with multiple transmit antennas are developed and evaluated in this paper. The system performance is investigated in terms of its effective signal-to-interference-plus-noise ratio (SINR), the achievable sum rate and the achievable rates with outage. And some further discussions regarding its advantage over conventional rake receivers and the impact of spatial correlations between users are given at the end of this paper. It is shown in both analytical and simulation results that desirable properties and satisfying performances can be achieved in the proposed TRDMA multi-user downlink system, which makes TRDMA a promising candidate for future energy-efficient low-complexity broadband wireless communications.

Time-Reversal Wireless Paradigm for Green Internet of Things: An Overview

“…The feasibility of applying TR technique into ultra-wideband (UWB) communications has been studied in [46]- [48] with the focus on the bit error rate (BER) performance through simulation. A system-level theoretical investigation and comprehensive performance analysis of a TR-based multiuser communication system was conducted in [25], where the concept of TRDMA was proposed. To improve the performance of the TRDMA systems, interference suppression through waveform design [27], [49] and interference cancelation [50] are proposed.…”

“…Typically, the symbol rate can be much lower than the system chip rate. 1 Therefore, a rate backoff factor is introduced to match the symbol rate with the chip rate by inserting zeros between two symbols [24], [25], [46], [60]. Applying the pulse shaping filter , Z and the transmitted signal 2 can be expressed as…”

“…Based on TR technique, we recently introduced in [25] a novel multi-user media access scheme, TRDMA, for wideband communication. Leveraging the unique temporal and spatial focusing effects of the TR technique [24], [61], the TRDMA exploits the spatial degrees of freedom of the environment and uses the multipath channel profile associated with each user's location as a location-specific signature for the user.…”

“…The theoretic analysis in [24] shows that a typical TR system has a potential of over an order of magnitude of reduction in power consumption and interference alleviation, which means that TR system can provide better battery life and support multiple concurrent active users. Moreover, with our proposed asymmetric TR architecture, only one-tap detection is needed at the receiver side [25], thus the computational complexity at the terminal devices is low, which means the cost of the terminal devices is also low. Note that the achievable rate can still be very high when the bandwidth is wide enough as shown in [26].…”

“…Note that the achievable rate can still be very high when the bandwidth is wide enough as shown in [26]. In addition, the TR system can easily support heterogeneous terminal devices by providing various QoS options through adjusting the waveform and backoff factor [25], [27]. Finally, the unique location-specific signature in TR system can provide additional physical-layer security and thus can enhance the privacy and security of customers in IoT [24].…”